User:Laurenpayne

There are 3 different types of galaxies in our Universe; Elliptical, Spiral, and Irregular. Elliptical galaxies and Spiral galaxies can be classified further using the "Tuning Fork". The Tuning Fork is a model of classification created by Edwin Hubble. He believed that it was an evolutionary sequence used for galaxies, as well as classification, which was eventually proved incorrect. He believed that Spiral galaxies start out as Ellipticals, and evolved into Spirals and flattened out and developed arms. Astronomers find today that actually sometimes Spirals evolve into Ellipticals.

Elliptical Galaxies are galaxies that have a shape of an ellipsoid, have a smooth, almost featureless appereance, and have no spiral structure or flattened disks. Elliptical galaxies constitute aproximatly 10% of observed galaxies. The masses of Elliptical Galaxies cover a large range, from about 10^7 to 10^13 solar masses.They are classified with a number that describes their appearance, adn denoted with the letter E. For example, and E0 is almost perfectly circular, while an E7 is quite elongated. They contain hundreds of millions to trillions of stars. They are also the biggest type of galaxy in the universe. Elliptical galaxies are the result of many collisions between smaller galaxies, and the collisions destroy delicate spiral structures.

Spiral Galaxies are the most common type of galaxy, about 20% of known galaxies, and look like spirals with long arms winding toward a bright bulge at the center. If you can clearly see the spiral shape, they are called "Face On Spirals". If you can only see the side view of the spiral, then they are called "Edge On Spirals". They are divided into three main types, denoted with the letter S, and the types are dependant on how tightly wound their spiral arms are. The classifications are Sa, Sb, and Sc. Another type of Spiral Galaxies are Barred Spirals, which have a band of bright stars emerging from the center and running across the middle of the galaxy. Spiral Galaxies are made of lots of gas, dust, and newly forming stars, and are among the brightest because of all the hot, young stars. Our own galaxy, the Milky Way, is a spiral galaxy.

The final type of galxies are Irregular Galaxies, which have little rotational symmetry in thier structure and no clearly defined shape or structure similiar to that of Ellipticals or Spirals. Irregular Galaxies constitute about 3% of known galaxies. Thier masses are about 10^8 to 10^10 solar masses, and have diameters ranging from 1 to 10 kpc. They have large amounts of gas, dust, and young stars. There are "normal" irregular galaxies and peculiar galaxies, which look unusual or abnormal in some respect. Many orbit larger galaxies. They are formed by collisions of galaxies, or when two galaxies are close and their gravitational forces interact. Some of the Irregular Galaxies are young and haven't yet reached a symetrical shape.